Relational Database Management System Mcqs

Page No. 1

State true or false: If a relation consists of a foreign key, then it is called a referenced relation of the foreign key dependency.


aTrue


bFalse


ceither true and false


dnone of these


View Answer False

Choose the option that correctly explains in words, the function of the following relational algebra expression σyear≥2009 (book ⋈ borrow)


aSelects all tuples from the Cartesian product of book and borrow


bSelects all the tuples from the natural join of book and borrow wherever the year is lesser than 2009


cSelects all the tuples from the natural join of book and student wherever the year is greater than or equal to 2009


dSelects all tuples from the Cartesian product of book and borrow wherever the year is greater than or equal to 2009



Statement 1: A tuple is a row in a relatioStatement 2: Existence of multiple foreign keys in a same relation is possiblen


aBoth the statements are true


bStatement 1 is correct but Statement 2 is false


c Statement 1 is false but Statement 2 is correct


dBoth the statements are false



What is the method of specifying a primary key in a schema description?


aBy writing it in bold letters


bBy underlining it using a dashed line


cBy writing it in capital letters


dBy underlining it using a bold line



An attribute is a __________ in a relation.


a Row


bColumn


c Value


dTuple


View Answer Column

What does the “x” operator do in relational algebra?


aOutput specified attributes from all rows of the input relation. Remove duplicate tuples from the output


b Output pairs of rows from the two input relations that have the same value on all attributes that have the same name


cOutput all pairs of rows from the two input relations (regardless of whether or not they have the same values on common attributes)


dReturns the rows of the input relation that satisfy the predicate



What action does ⋈ operator perform in relational algebra


aOutput specified attributes from all rows of the input relation and remove duplicate tuples from the output


bOutputs pairs of rows from the two input relations that have the same value on all attributes that have the same name


c Output all pairs of rows from the two input relations (regardless of whether or not they have the same values on common attributes)


dReturn rows of the input relation that satisfy the predicate



What is a foreign key?


aA foreign key is a primary key of a relation which is an attribute in another relation


b A foreign key is a superkey of a relation which is an attribute in more than one other relations


cA foreign key is an attribute of a relation that is a primary key of another relation


d A foreign key is the primary key of a relation that does not occur anywhere else in the schema



What is an Instance of a Database?


a The logical design of the database system


bThe entire set of attributes of the Database put together in a single relation


cThe state of the database system at any given point of time


dThe initial values inserted into the Database immediately after its creation



Choose the correct statement regarding superkeys


aA superkey is an attribute or a group of multiple attributes that can uniquely identify a tuple


bA superkey is an attribute or a group of multiple attributes that can uniquely identify a tuple


c Every superkey is a candidate key


dA superkey is an attribute or a set of attributes that distinguish the relation from other relations\



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